1. Field of the Invention
The present invention relates to a liquid crystal display (LCD) device and a driving method thereof, and more particularly, to an LCD device that can control a viewing angle and improve brightness of an image, and a driving method thereof.
Liquid crystals (LCs) have dielectric anisotropy and refractive index anisotropy. The arrangement of molecules of the LCs varies according to an electric field applied thereto with the polarization of light changing according to the arrangement. An LCD device applies an electric field to LCs having dielectric anisotropy and refractive index anisotropy to control light transmittance through the LCs to thereby display an image.
FIG. 1 is a view of a related art LCD device.
Referring to FIG. 1, the LCD device includes an upper substrate 11 including a color filter array 19, and a lower substrate 1 including a thin film transistor (TFT) array 9, the upper substrate 11 and the lower substrate 1 being attached to face each other, and LCs 16 filling cell gaps disposed between the two substrates 11 and 1.
The color filter array 19 includes a black matrix 12, a color filter layer 13, an overcoat layer 14 for planarizing the upper substrate 11, and a common electrode 15 for forming an electric field in cooperation with a pixel electrode 7. The color filter array 19 further includes an upper alignment layer for uniformly aligning the LCs 16.
The TFT array 9 includes gate lines 2 and data lines 3 crossing each other to define pixels on the lower substrate 1. Each pixel of the array includes a TFT 6 connected to a gate lines 2 and a data line 3, and a pixel electrode 7 connected to the TFT 6. The TFT array 9 further includes a lower alignment layer for uniformly aligning the LCs 16.
The TFT 6 supplies a data signal from the data line 3 to the pixel electrode 7 in response to a gate signal from the gate line 2. An electric field is generated between the pixel electrode 7 to which the data signal has been supplied through the TFT 6, and the common electrode 15 to which a reference voltage has been supplied. The light transmittance of the LCs 16 arranged between the lower substrate 1 and the upper substrate 11 is controlled by this electric field to display an image.
The LCD device has been developed to improve a viewing angle characteristic so that an image can be viewed from any direction. However, providing a wide viewing angle has the side effect of allowing the leakage of private information in applications in which a computer system is used for private purposes or in security-oriented businesses such as performing tasks at a bank.
Accordingly, there is a need to develop an LCD device that can selectively control a viewing angle. In other words it is desired to develop an LCD providing a wide viewing angle mode allowing an image to be viewed to a user at various viewing angles, and providing a narrow viewing angle mode limiting displaying an image to a user at a specific viewing angle.